Temperature Induced Phase Transition of Encapsidated Phage DNA

Double-stranded DNA bacteriophages are highly stressed under the high internal pressure that is described as stored energy. Most of them eject their genome into the host bacteria via receptor binding. In the previous work, isothermal titration calorimtery (ITC) was used, for first time, to directly measure the heat released during DNA ejection from the phage lambda, triggered in solution by solubilized LamB receptor. In the current study, using ITC, we investigate the ejection energy from the capsid of phage lambda packaged with 94-110% genome, at a wider temperature range between 18 and 40°C. We experimentally show that DNA undergoes phase transition when exposed to different temperatures. The event of phase transition was also confirmed by differential scanning calorimetry (DSC). (Less)